Zombieants.ca is a science blog dedicate to the discussion of parasites, parasite altered behaviour with a specific focus on research by our lab group into the parasite Dicrocoelium dendriticum.
Dicrocoelium dendriticum is a species of parasitic flatworm belonging to the group of animals known as Trematoda, this group includes flatworms, flukes and tapeworms. It is commonly referred to as the “lancet liver fluke” due to its long slender shape and as this name suggests it parasitizes the livers of a variety of animals. It is a small fluke roughly two cm in length which allows it to live in the bile ducts of hosts livers. This causes irritation and blockage of the ducts leading to inflammation and cirrhosis of highly infected livers.
Dicrocoelium can be found throughout the world, usually in higher and dryer environments. The life cycle involves three different hosts, snails, ants and grazing mammals. Adults shed eggs in the feces which are ingested by snails. Here the parasite develops and multiplies, asexually, until the snail eventually encases the growing mass of parasites in mucous and releases a “slime ball” from its respiratory pore. These slime balls are then eaten by ants whereby they become infected. The majority of the parasites move to the abdomen of the ant and form protective cysts. Amazingly, one of these parasites bucks the trend and will move through the body to the ant’s brain and physically wrap around it. Infected ants then display altered behaviour giving them the name zombie ants. During cooler parts of the day the ants will climb up vegetation and lock on with their mandibles, remaining there until the temperature becomes deadly to the ant host. Then and only then does the parasite relinquish control and allow the ant to release. This behaviour increases the exposure of the parasite to the final host, grazing mammals, which become infected by accidentally ingesting the clinging ants.
Another interesting feature of the Dicrocoelium life cycle is its ability to use different species at each stage. Multiple species of snail, ant and mammal can be infected throughout the world and may be one of the reasons that have allowed it to spread throughout the world. Dicrocoelium was confirmed to be in North America in the 1950s and it is believed to have come from Europe. It is also found in North Africa and parts of Asia. Our lab group in Lethbridge discovered it in the Cypress Hills region of Alberta in the early 2000s after reports surfaced in the 1990s. Since then it has increased in prevalence and now infects four species of final host in the area: cattle, elk, mule and white tail deer. Since its discovery here in Alberta the Goater lab from the University of Lethbridge has been researching different aspects of its biology, distribution and epidemiology.
Many aspects of this research would not be possible without collaborations with the Gilleard lab group at the University of Calgary. There are currently three graduate students working on this system in the (see our links pages for links to both the Goater and Gilleard labs pages). There projects range from identifying novel proteins for use in sero-diagnostics, using GIS modeling to identify risk factors involved in predicting the presence of the infective stage of the parasite and developing molecular markers to study the transmission of this parasite among the different species of final hosts and determine where the Dicrocoelium in Alberta originated.
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